The invention discloses a self-intake type air cylinder and an air compressor provided with the self-intake type air cylinder. The self-intake type air cylinder comprises an air cylinder body. The air cylinder body comprises a cylinder barrel, a piston and a seal ring. The piston conducts reciprocating motion in the cylinder barrel. The piston is sleeved with the seal ring. The piston and the cylinder barrel are in close fit through the seal ring. An included angle is formed between the axial direction of the seal ring and the motion direction of the piston. The cylinder barrel is provided with an air outlet. The air outlet is provided with a one-way valve. The self-intake type air cylinder comprises the cylinder barrel, the piston and the seal ring; the piston conducts reciprocating motion in the cylinder barrel; the piston is sleeved with the seal ring; the piston and the cylinder barrel are in close fit through the seal ring; the included angle is formed between the axial direction of the seal ring and the motion direction of the piston, namely the seal ring and the cylinder barrel are arranged in a relatively tilting mode. As a result, when the piston is pulled out till one edge of the seal ring breaks away from one edge of the cylinder barrel, air enters the cylinder barrel through the position. By means of the self-intake type air cylinder, an air inlet unit does not need to be additionally arranged on the cylinder barrel, therefore, the structure is simpler, the weight is lowered, the size is reduced, and miniaturization and portability of the portable air compressor are facilitated.